As Latin America asserted its diplomatic and economic autonomy from the United States over the past decade, Colombia was consistently seen as the outlier – a lackey of the US, which has invested billions in the antidrug Plan Colombia. Colombia had scant credibility among those who sought a more unified – and independent – voice for Latin America.

Building consensus among Latino nations is particularly important today, at a time when many say the region is plagued by high rates of crime and insecurity. But the challenges facing Latin America are the problems of the north as well, and a leader who can bridge key differences between the political extremes regionally, as well as with the US, is key to taking on daunting issues such as the trafficking of drugs and weapons.

"Santos has taken several steps to assert Colombia's position regionally and globally," says Arlene Tickner, a political analyst at the University of the Andes in Bogotá, Colombia. So far, she says, he is proving to be adept in the role. "He is much more efficient in trying to create bridges between the left and the right in the region."

When Mr. Santos was elected president in 2010, few believed he would veer from the path of his predecessor and former boss, Álvaro Uribe, who moved Colombia closer to the US with his hard-line security views. Santos served as defense minister under Mr. Uribe, raising concerns about his human rights record. But by many accounts, he has brought more transparency to local institutions. And his shift away from the US was evident early; in his inaugural address, he said he would prioritize relations with Venezuela and Ecuador – and didn't even mention his large neighbor to the north.

"In a relatively short period of time, he totally put into reverse Colombia's traditional policies," says Larry Birns, head of the Council on Hemispheric Affairs. Among those policies, he says, was Colombia's strong pro-US stance, hostility toward Venezuela, support for the Plan Colombia model of fighting the drug war, and hard-line security policies.

Santos has not only pushed Colombia closer to the center, analysts say. He has also sought to unify countries on opposite ideological spectrums, mending the tense bilateral relationship with Venezuela, while most recently defusing a standoff between the US and leftist leaders who were promising to boycott the OAS summit if Cuba, which does not belong to the group, was not at the table.

"There are sharp divisions [in Latin America], and the region … is moving in different directions," says Michael Shifter, president of Inter-American Dialogue. "If you are going to deal with the main regional problem, which is citizen security, you have to work together…. There is a real need," Mr. Shifter says.

Deft resolution to Cuba controversy

The brouhaha over Cuba's participation in the regional summit is, in many ways, a microcosm of the divides that have grown in the Americas in the past decade.

Cuba has not been part of the OAS since 1962. But Ecuadorean President Rafael Correa rallied the Bolivarian Alliance of the Americas, a bloc of left-leaning nations, to protest Cuba's exclusion by possibly not showing up to the 34-nation meeting. Cuba's presence could have, in turn, led to a US boycott.

Santos flew to Havana and brokered a resolution: Cuba is not invited to the summit, yet the country's future inclusion will be on the agenda.

Prior to the Cuba-OAS standoff, Santos helped broker the return of Honduras to the OAS after it was expelled for the 2009 ousting of former President Manuel Zelaya. He has also traveled extensively, trying to export Colombia's security know-how, after leadership reined in decades of kidnapping and violence fueled by battles among leftist guerrillas, right-wing paramilitaries, and the state. Santos has also joined sitting presidents in supporting a robust debate on drug legalization, a clear deviation from US policy.

Santos is not the first person to try his hand as a regional diplomat, of course. Venezuela's president, Hugo Chávez, sought the same role for the early part of the past decade, rallying countries through his anticapitalist rhetoric and oil-revenue-generated international aid packages. But his vitriolic anti-Americanism has led many to distance themselves from him.

Brazil – with its sheer size, making up nearly 50 percent of South America, and its economic influence as a powerful emerging market – is a logical leader for the region. The country has gone further than most nations in the Americas on the international stage, and has been a strong regional leader in the past, particularly under former President Luiz Inácio Lula da Silva.

But its sustained economic growth has created an asymmetry with the rest of Latin America, says Joao Augusto de Castro Neves, a Latin America analyst at the Eurasia Group. In addition, the country is constrained by language – it is the only country in the region that uses Portuguese – and a historic fear of being perceived as imperialist by its neighbors, Mr. Castro Neves says. And Brazil's current president, Dilma Rousseff, isn't a career politician and has proved to be less interested in diplomacy. "Rousseff doesn't pay a lot of attention to foreign policy," Castro Neves says. "She's focused on domestic politics more and lets the foreign ministry take care of most of the diplomacy."

The regional leadership some see in Santos can help overcome mistrust and political differences in order to find solutions for the Americas' most pressing issues.

Moving any regional agenda forward has been an increasingly difficult task over the past decade, says Eric Farnsworth, vice president of the Council of the Americas, who worked on the first Summit of the Americas in Miami in 1994. For example, in the early 1990s, he says, the region was unanimously united over free trade, but that is now such a divisive issue – and perceived to be an "American" neoliberal policy – that it cannot even be broached.

Most recently, a boycott from either the US or left-leaning countries siding with Ecuador in the Cuba-OAS case last month would have been an embarrassment to Colombia.

Though Santos has the will to step up as a leader, even likening himself to former US President Bill Clinton, according to Shifter, he is also the beneficiary of a changing political climate that allows for someone with his skills and background to step into the limelight. Relations with the US are better now than they were in the past decade, and President Obama is personally liked in the region. As a result, Colombia's relationship with the US is less of a political liability, especially, Castro Neves says, because a more centrist vision is taking root in the Americas as a whole. "[The region] is much less radical today in its foreign policy than it was just a few years back," he says.

"I'm optimistic because leaders are meeting more, communicating more, sharing information more, and proposing policies that they share," says Roberto Izurieta, head of the Latin America Department at The George Washington University's Graduate School of Political Management.

For success, Mr. Izurieta says, "you just need the minimum of working together with your neighbors and establishing a plan."